Single amino acid substitution in human platelet glycoprotein Ibbeta is responsible for the formation of the platelet-specific alloantigen Iy(a)

We recently described a new low-frequency platelet alloantigen on the human platelet glycoprotein (GP) Ib-IX complex, termed Iy(a), which was implicated in a severe case of neonatal alloimmune thrombocytopenia. Immunoprecipitation studies with trypsin-treated platelets indicated that the Iy(a) alloantigenic determinants are formed by the membrane-associated remnant moiety of GP Ibalpha (GP Ibalpha(r)) together with GP Ibbeta and GP IX. To elucidate the molecular basis underlying the Iy(a) alloantigen, we amplified GPIbalpha(r), GPIbbeta, and GPIX genes by polymerase chain reaction (PCR). Nucleotide-sequence analysis of these 3 genes showed a G to A transition at position 141 on GPIbbeta gene in a subject positive for Iy(a). This transition resulted in a Gly(15)Glu dimorphism on the N-terminal domain of GPIbbeta. This finding was confirmed by genotyping analysis of 6 Iy(a)-positive subjects by restriction fragment length polymorphism (RFLP) studies using NarI endonuclease. In 300 randomly selected healthy blood donors, one Iy(a)-positive individual was found. Phenotypes determined by monoclonal antibody-specific immobilization of platelet antigens assay and genotypes determined by RFLP were identical in this population. Analysis of Iy(a)-positive platelets showed that the point mutation affected neither the degree of surface expression nor the function of the GP Ibalpha-GP Ibbeta-IX complex on the platelet surface. Transient expression of the GP Ib-IX complex in CHO cells using wild-type GP Ibbeta (Gly(15)) or mutant GP Ibbeta (Glu(15)) allowed us to demonstrate that this single amino acid substitution is sufficient to induce Iy(a) epitope(s). (Blood. 2000;95:1849-1855)     

Prevention of contamination of oral rehydration fluids

A treated city water supply and most waters tested from several tourist hotels in a popular international resort were found to be microbiologically safe for drinking, but untreated domestic water supplies and locally prepared soft drinks frequently had high levels of bacterial contamination and faecal pollution. A novel oral rehydration mixture, based on fruit juice cordial which kills intestinal bacteria in vitro, was effective for treating young children with diarrhoea and mild to moderate dehydration in the same environment.     

The in vitro activity of Midecamycin against various Vibrio species.

The susceptibility of various Vibrio species to Midecamycin was studied by the tube dilution method. A MIC of 100 mug per ml of Midecamycin in BHI broth was taken as an indicator of bacterial resistance. All Vibrio cholerae classic biotype strains tested, were sensitive to Midecamycin. In respectively, 87.4%, 60.7% and 89.5% of Vibrio cholerae El Tor biotype, Vibrio parahaemolyticus and Vibrio NAG strains tested, were sensitive to Midecamycin.     

Identification of the Yukb Allo-Antigen on Platelet Glycoprotein IIIa

The glycoprotein (GP) localization of a new platelet-specific allo-antigen Yukb is described. The antibody was isolated from serum of a patient with neonatal allo-immune thrombocytopenia. In immunoblot procedure, it bound exclusively to platelet GP IIIa, like anti-PlA1, while the known anti-Baka and anti-Leka reacted with GP IIb. Analysis of GP from chymotrypsin-treated platelets with anti-Yukb revealed no binding in the 68-kilodalton position while anti-PlA1 did. Thus, unlike the PlA1 antigen, the Yukb determinant either resides on the 30-kilodalton fragment of GP IIIa or it is destroyed by chymotrypsin treatment.     

Report on the 15th International Society of Blood Transfusion platelet immunology workshop

Background and Objectives The aim of the 15th ISBT Platelet Immunology Workshop was to evaluate the detection of free platelet‐reactive autoantibodies from ITP patients by the use of a standardized MAIPA protocol, to compare sensitivity and specificity of antibody detection for anti‐HPA‐1a and serologically difficult‐to‐assess antibodies against HPA‐3, to identify whether anti‐HPA‐1a titration results can be compared between laboratories, and to evaluate HPA genotyping methods. Materials and Methods Workshop materials were shipped from the organizing laboratory in Giessen, Germany. Thirty laboratories from 19 countries participated. Results Results for the detection of autoantibodies differed greatly between the laboratories and no consensus was reached for one of the two sera. Detection and titration of antibodies against HPA‐1a, in contrast, gave largely congruent results. Serologically difficult‐to‐assess antibodies recognizing HPA‐3a and HPA‐3b were not detected by many laboratories. For genotyping, good agreement was achieved. Conclusions Detection of HPA‐1a antibodies, titration of anti‐HPA‐1a, and HPA genotyping are well performed in most participating laboratories. The workshop has identified two specific areas with room and need for improvement: the detection of autoantibodies and the detection of HPA‐3 alloantibodies. Recommendations of the Working Party on techniques that can help to overcome these problems are desirable.     

Maternal antibodies against paternal class I human leukocyte antigens are not associated with foetal and neonatal alloimmune thrombocytopenia

The causative role of maternal, anti-human leukocyte antigen (anti-HLA) class I antibodies in foetal and neonatal alloimmune thrombocytopenia (FNAIT) remains controversial. Furthermore, in FNAIT cases caused by anti-human platelet antigen-1a (anti-HPA-1a) antibodies, the possible additive effect of maternal anti-HLA class I antibodies on outcomes is unclear. Among 817 mother–father–neonate trios of suspected FNAIT, we assessed the possible association of maternal anti-HLA class I antibodies with neonatal platelet count, and the incidence of FNAIT caused by anti-HPA-1a antibodies. In 144 FNAIT cases caused by anti-HPA-1a antibodies, we investigated the possible association of maternal anti-HLA class I antibodies with neonatal platelet count, birth weight, and the incidence of intracranial haemorrhage (n = 16). Maternal anti-HLA class I antibodies were not associated with neonatal platelet count in suspected cases of FNAIT. There was no significant interaction between the presence of anti-HLA class I antibodies and anti-HPA-1a antibodies. In FNAIT cases caused by anti-HPA-1a antibodies, there was no association between the presence of anti-HLA class I antibodies and neonatal platelet count, birth weight, or occurrence of intracranial haemorrhage. This study’s findings do not support the concept that maternal anti-HLA class I antibodies represent a risk factor of FNAIT or disease severity.